1. Field of the Invention
The present invention relates to an electric rotary shaver and more particularly to an electric rotary shaver in which a cutter retaining plate that supports the inner and outer cutters is detachably attached to an outer cutter frame.
2. Prior Art
Various types of electric rotary shavers have been proposed, and FIG. 6 shows an example of an electric rotary shaver that is equipped with three rotary cutters.
In this electric rotary shaver, a shaver head 20 is detachably mounted to the upper portion of a main body case 10 of the shaver. The shaver head 20 includes three cutter units 22 that are arranged so that the centers of the cutter units 22 are positioned at the vertices of an (imaginary) equilateral triangle. Each of the cutter units 22 comprises an outer cutter 24, an outer cutter case 26 and an inner cutter; and in the shown electric rotary shaver, the cutter units 22 are movable in an arbitrary direction with respect to the outer cutter frame 30 of the shaver head 20.
FIGS. 7 and 8 are explanatory diagrams that show the internal structures of the shaver heads in conventional electric rotary shavers. More specifically, FIGS. 7 and 8 show cutter retaining plates 32 that support the cutter units and are detachably attached to the outer cutter frames 30.
In the shaver shown in FIG. 7, the cutter retaining plate 32 that supports the cutter units 22 (each comprising the outer cutter 24, outer cutter case 26 and inner cutter 28) is screw-fastened to the outer cutter frame 30. More specifically, a mounting screw 34 is rotatably held in the cutter retaining plate 32, a female screw projection 36 into which the mounting screw 34 is screwed is formed in the inside surface of the outer cutter frame 30, and the cutter retaining plate 32 is attached to the outer cutter frame 30 by turning the mounting screw 34.
The outer cutter frame 30 is comprised of a side frame portion 30a and a top frame portion 30b. The top frame portion 30b is formed in a continuous fashion from the side frame portion 30a that engages the main body case 10 of the shaver, and three circular cutter unit holes that receive the cutter units 22 are formed in the top frame portion 30b. The female screw projection 36 is provided in the center 30c of the top frame portion 30b. The mounting screw 34 is also provided in the center of the cutter retaining plate 32 so as to positionally correspond to the female screw projection 36.
By screw-fastening the cutter retaining plate 32, in which the cutter units 22 have been mounted, to the outer cutter frame 30, the shaver head 20 having the projected cutter units 22 as seen from FIG. 6 is obtained. The shaver head 20 thus assembled is mounted to the upper portion of the main body case 10 of the shaver.
In the shaver shown in FIGS. 8A and 8b, a fastening plate 38 is rotatably attached to the cutter retaining plate 32, and a mounting projection 40 is formed vertically on the inside surface of the outer cutter frame 30. The fastening plate 38 is attached to the outer cutter frame 30 by way of engaging an engagement edge 40a formed at the tip end of the mounting projection 40 with the fastening plate 38.
As seen from FIG. 8B, the engagement edge 40a is shaped substantially in triangle when viewed from the end. In the fastening plate 38, an engagement opening 38a is formed so that the engagement edge 40a of the mounting projection 40 is inserted. The engagement opening 38a is also in a triangular shape so as to correspond to the shape of the engagement edge 40a. 
When the cutter retaining plate 32 is to be attached to the outer cutter frame 30, the outer cutter frame 30 and cutter retaining plate 32 are positioned with the engagement edge 40a of the outer cutter frame 30 protruding from the engagement opening 38a. Then, the fastening plate 38 is turned, so that the engagement edge 40a and the fastening opening 38a are brought into a shifted positional relationship as shown in FIG. 8B, thus making an engagement. As a result, the cutter retaining plate 32 is attached to the outer frame 30.
When the cutter retaining plate 32 is to be detached from the outer cutter frame 30, the fastening plate 38 is rotated so that the engagement between the engagement edge 40a and the engagement opening 38a is released. Then, the cutter retaining plate 32 is pulled away from the outer cutter frame 30.
The reason that the cutter retaining plates 32 are detachably attached to the outer cutter frames 30 in electric rotary shavers is to allow removal of the cutter retaining plate 32 from the outer cutter frame 30 so that the inner cutters can be replaced. Accordingly, in the attachment-detachment mechanism which is used to attach and detach the cutter retaining plate 32 to and from the outer cutter frame 30, it is preferred that the attachment-detachment operation be done simply and the mechanism therefor be not complicated.
In this respect, the structure shown in FIG. 7 in which the cutter retaining plate 32 is screw-fastened to the outer cutter frame 30 with the mounting screw 34 has some problems. The operation to tighten and loose the mounting screw 34 by turning it must be performed each time the attachment-detachment is needed, and such an attachment-detachment cannot be done by a one-touch operation. Thus, the operation is bothersome.
On the other hand, in the structure that uses the fastening plate 38 as shown in FIGS. 8A and 8B, the attachment-detachment can be accomplished in a one-touch operation merely by rotating the fastening plate 38 by approximately one-half turn. Accordingly, the operation is simple. However, because the mounting projection 40 extends a considerable distance from the outer cutter frame 30, the strength and moldability of the mounting projection 40 becomes the problem.
The present invention solves the above-described problems with the prior art electric shavers.
It is, therefore, an object of the present invention to provide an electric rotary shaver in which the cutter retaining plate can be attached to and detached from the outer cutter frame by a one-touch operation, thus improving the operation of attaching and detaching the cutter retaining plate to and from the outer cutter frame.
It is another object of the present invention to provide an electric rotary shaver that involves a simple structure, uses internal space efficiently and has an improved operability.
The above objects are accomplished by a unique structure for an electric rotary shaver in which a cutter retaining plate equipped with cutter units each comprising an inner cutter and an outer cutter is detachably attached to an outer cutter frame; and in the present invention, the shaver further includes an attachment-detachment mechanism for attaching and detaching the cutter retaining plate to and from the outer cutter frame, and the attachment-detachment mechanism is comprised of:
a boss in the shape of a triangular tube having engagement openings formed in side surfaces thereof, and
an engagement projection to be inserted in the boss so that when the engagement projection is in the boss and rotated relative to the boss, comer portions of the engagement projection are engaged and held in the engagement openings; and
the boss is provided on the outer cutter frame and the engagement projection is provided on a mounting knob that is held in the cutter retaining plate.
In this structure, the boss can be provided on the mounting knob instead of on the outer cutter frame, and the engagement projection can be provided on the outer cutter frame instead of on the mounting knob.
In addition, when the boss or the engagement projection is provided in the outer cutter frame, the boss or the engagement projection is provided on a connecting section of the top frame portions of the outer cutter frame.
Furthermore, the mounting knob held in the cutter retaining plate is provided so that it is rotatably inserted in a through-hole formed in the cutter retaining plate.
In the electric rotary shaver of the present invention, the outer cutter frame is formed with three cutter unit holes for respectively receiving the cutter units therein so that the top frame portions extend from the connecting section in three branches; and the boss is provided on the connecting section so that the side surfaces of the boss are parallel to the cutter unit holes, and the engagement projection is provided at the tip end of the mounting knob. Instead, the engagement projection can be provided on the connecting section, and the boss is provided at the tip end of the mounting knob.
Furthermore, in the electric rotary shaver of the present invention, a spring that elastically presses against the engagement projection can be provided on the bottom of the boss, and a stopper that prevents the mounting knob from slipping out of the cutter retaining plate can be provided on the mounting knob.